As a 30 year carpenter (20 years union) I am pretty accurate with a power saw but some times accuracy counts more than others. No matter how close you pay attention to your cut line sometimes the blade has a mind of its own.
If accuracy counts (cutting frp or plywood for your walls or facing those cost saving home built cabinets) this saw guide gig will make you look like a pro.
I did mine out of 5/8 plywood. You can go down to 1/2 or 3/8 but 3/4 would be even better. Identify the cleanest factory edge then rip off about 2 to 3 inches (cut does not need to be perfect, factory edge is the key)
Now take a chalk box and strike a line across the length of the remaining plywood. Now starting at one end screw your rip piece of plywood to the larger board. First screw one inch in then a screw every 6 to 8 inches. Move your rip back and forth to insure it is on your chalk line at the screw you are putting in.
Final step is to take your power saw and cut the entire length of your attached rip "fence".
Now when you need to make a critical long cut you line your gig up to your measurement lines and use clamps to hold your gig to the material you are cutting and know every cut will be straight. Make sure your screws did not go all the way through. If they did a grinder or file will take care of insuring the bottom is smooth
I made mine 8 ft long but you can make them any length you want/need (over 8 ft requiring 2 base boards gets hairy though)
Note: when lining up the gig remember to have the gig over the side you intend to use because nothing will ruin your day more than making a cut on a $100+ piece of plywood and finding out you are a blade short on your cut
